This occurs mostly in the Great Plains, and is virtually unknown in eastern states. In Ky. the only recorded site is based on Cranfill's coll. (1991) from a calcareous glade of HARD (KY). The coll. matches var. floribunda (Nutt. ex Torr. & Gray) Rydb. (within Psoralea), a robust form not recognized in recent treatments. Plants had disappeared at the site for ay years, perhaps due to additional collecting by fabophiles, but the population was rediscovered in recent years by T. Littlefield (KSNPC). P. tenuifolium is a "wild alfalfa" with deep, spreading, edible roots that may promote association with buffalo wallows and other animal disturbance (Gibson 1989). The species has been placed in the widespread western genus, Pediomelum by Egan & Crandall (2008). Other species of this genus are somewhat disjunct in southeastern states, including P subacaule (T&G.) Rydb. of central Tenn., n . Ala. and n. Ga. (K, W).